The invention relates to a tool for cutting out motor vehicle windscreens.
Until now, motor vehicle windscreens, in particular front screens, were usually removed either with an oscillating knife or with a thin steel wire which exhibits a handle at each end.
The oscillating knife has the disadvantage that it cannot be used universally since the rubber seals or beads of adhesive to be cut are sometimes very thick and the knife can easily tilt and break, in particular in the radiused corners. In practice, this makes it necessary to purchase more knives fairly often, which is a considerable financial outlay. In addition, a costly oscillation machine and a power supply are required. The danger of injury due to incorrect use must not be underestimated.
With the wire design it is disadvantageous that two persons are required to carry out the work: one inside the car to hold the wire, and a second outside to guide the wire around the screen with continuous pulling and releasing movements, similar to sawing, after it has been passed through the bead of adhesive.
In addition, a device for removing vehicle windscreens is known from U.S. Pat. No. 5,622,093 or the Equalizer brochure, page 18 or 27 under the name xe2x80x9cSide Winderxe2x80x9d. This device exhibits a suction cup which can be activated by means of a vacuum pump and secured to the windscreen on the inside. Secured rotatably to the upper side of the pot-shaped housing of the suction cup there is a rotating head which in turn is attached to a relatively long tension spring which is connected to the inner end of a cutting wire. When cutting, the wire passed through the bead of adhesive or seal is repeatedly pulled radially and released by means of a handle on the outside, through which the tension spring is correspondingly stretched and relaxed. As a result, the cutting wire describes a radial sliding movement in relation to the suction cup which movement, together with a tangential advance movement, produces a sawing cutting movement or action. As the rotating head is arranged on the upper outer side of the housing offset and therefore a relatively long distance axially from the active suction side, the result is a relatively high tipping moment when under tensile load and also under its own weight, for which reason a relatively high suction force is required which is applied by the vacuum pump. This entails a relatively complex structure for the suction cup itself and means that corresponding vacuum connections must be available at all times. In addition, the long tension spring is relatively a nuisance as when it is loose it sags under its own weight and can cause damage.
The object of the invention is to provide a tool of the kind named above which is simple and reliable in design and handling and can be operated purely by hand without additional equipment or vacuum connections.
Accordingly, the spring arranged between the rotating head and the cutting wire is a compression spring which is located between an outer tangential spring supporting wall and a wire holder displaceable radially inside the latter. In addition, the wire is connected to the wire holder so that the spring is compressed when the wire is pulled, and relaxed when the wire is released, during which the holder is displaced radially inwards and pulls the wire radially inwards. The active part, namely the spring, is now in the form of a compression spring and arranged radially inside the wire attachment point of the rotating head. When the wire is released, the spring is also released so that it is relaxed radially inwards with the result that when it is relaxed, the spring no longer sags downwards with the outer end of the cutting wire under its own weight, but the cutting wire remains supported uniformly at all times by the spring supporting wall through which it is passed.
It is particularly advantageous when a conventional hand-operated suction cup is used which exhibits a relatively low pot-shaped housing on the upper outer side of which the actuating lever for producing the necessary suction vacuum is provided. The use of a hand-operated suction cup has only become possible because no large heavy tension spring is needed any more.
According to the invention, the rotating head can be an arm which is secured rotatably to the upper side of the housing and extends radially and on the outer end of which the spring supporting wall is provided essentially extending perpendicularly upwards or preferably downwards. The wire holder takes the form of a disc the diameter of which is equal to or greater than the diameter of the spring, and the wire passed through spring and then through the spring supporting wall is secured centrally to the disc and passed through the wall. This allows a design which is very simple but more reliable in operation when a rod passed slidingly through the supporting wall is secured to the disc, and the wire is attached changeably to the end of the rod extending radially outwards through the disc. Thus, the spring is arranged concentrically around the rod and at the same time located between the disc and the supporting wall and is pressed against the supporting wall by means of the disc when the wire is pulled, and when released, the spring pushes the disc radially inwards and draws the rod with the wire attached to it inwards. The fact that the supporting wall preferably faces axially downwards towards the disc means that the point of attachment of the wire is moved axially very close to the windscreen so that the tipping moment is reduced by the maximum amount and thus the suction force of the suction cup need not be so high.
It is particularly advantageous when the rotating head is a rotating collar which sits concentrically on the external circumference of the suction cup housing so that it is displaceable pivotably but immovable axially, and the lower front face of the collar can lie on the motor vehicle windscreen when the suction cup is firmly secured. The fact that the rotating collar lies on the windscreen means that additional axial support is provided.
The spring supporting wall can be a continuation of the rotating collar extending axially upwards so that the entire compression spring assembly is located inside the diameter of the rotating collar so that an extremely compact space-saving embodiment is provided.
However, the spring supporting wall can also be arranged offset radially outwards on the outside circumference of the rotating collar and form a spring housing together with at least one radial supporting arm. Thus, the compression spring with the wire holder is located between the outside circumference and the spring supporting wall and is also supported laterally or axially on the at least one radial supporting arm. The fact that only tiny sawing movements have to be performed by the wire means, the compression spring can also be relatively short so that the radially projecting spring housing can be made relatively short with the result that its volume is not a nuisance as regards handling and storage.
It is advantageous when the wire holder takes the form of a plate slide which is displaceable in the spring chamber radially in relation to the suction cup and guided axially in relation to the spring.
When the wire holder slide is no longer connected directly to the wire passed through the spring supporting wall, but connected to a rod which is passed through the supporting wall and on the projecting end of which the wire is secured, then the slide-shaped wire holder is embodied like a piston which exhibits reliable operation.
Advantageously, the spring housing is provided with a wall which sits on the outer circumference of the rotating collar with a U-shape and forms a spring chamber in which the spring piston is then located. Here, the spring chamber can be closed all around, i.e. exhibit walls so that a spring housing is produced, with the result that the moving parts, namely the spring and wire holder, are encapsulated on the outside and shielded against dirt. At the same time, the danger of accident is largely reduced as jamming of fingers for example between the moving parts is prevented by the encapsulation. Here, the spring housing can exhibit a rectangular cross-section or be cylindrical according to the diameter of the compression spring used.
According to a further advantageous embodiment, the rotating head can also be a narrow rotating ring which is arranged rotatable centrally and immovable axially on the outer surface of the suction cup housing. The piston rod of a spring cylinder is secured on this rotating ring so that it projects radially, so that the spring supporting wall is the piston of the cylinder while the wire holder is the cylinder through whose radially inner end wall the piston rod is passed, and on the inside the spring is supported on one side on this end wall. The spring is arranged between the inner end wall and the piston of the cylinder while the outer wall of the cylinder is used to secure the cutting wire. This spring cylinder can also be very short and compact, with only a very short spring stroke, so that overall a space-saving and at the same time reliable design is also provided here.